state of the science on cogeneration of heat and power from · pdf file ·...

J. (Jim) E. Smith, Jr., D.Sc., BCEEMUSEPA's Pathogen Equivalency Committee

Andrew W. Breidenbach Environmental Research Center Cincinnati, Ohio 45268smith.james@epa.gov

State of the Science on Cogeneration of Heat and Power from Anaerobic Digestion of

Municipal Biosolids

Metropolitan Water Reclamation District of Greater ChicagoJuly 31, 2009

What Will be Discussed?

• Energy Issues & Wastewater Treatment• Digester Feed

SourcesPreparation

• Digester OperationGas Production

• Combined Heat and PowerGas CleanupPower ProductionHeat Recovery

• Case Studies• New WEF/WERF/EPA Solids Manual

Significance and Drivers• Electric use for centralized W&WW treatment

accounts for 3.0%* of US electricity use $4 billion annually, 25-30% of total plant O&M Cost**

• Direct US GHG Emissions (2006)*** - Municipal WW treatment-

0.4 % of total GHG emissions3.0% of total anthropogenic Methane (CH4) and 2.2% of total Nitrous Oxide (N2O) emissions CH4 : 16 Tg CO2 eq., N2O: 8.1 Tg CO2 eq.

• Estimated US GHG Emissions (2006) from electricity generation for centralized W&WW treatment: 69.8 Tg CO2 eq. **** (1.2% of total US GHG emissions)

* Electric Power Research Institute (EPRI)** Energy Star Program*** Inventory of Greenhouse Gas Emissions and Sinks: 1990 – 2006, EPA, 2008**** EPRI estimate & Inventory of Greenhouse Gas Emissions and Sinks: 1990 – 2006, EPA, 2008

Aeration - 52 %

Misc. - 3%Pumping -

12 %

RAS pumping -3 %

Sludgeprocessing - 30%

Figures shown are typical for activated sludge plants, which use approximately 1200 kWh/MG treated.

Energy Used in Wastewater Treatment

Energy Conservation Measures

Solids Handling• Improved digester heating and

mixing• New dewatering equipment• Improved methods of drying

(including using anaerobic digester gas)

• Increased recycle (land application and recycled products)

OCSD Biosolids Management2008 Performance Report

Summary of OCSD Biosolids Disposal Options

Net Carbon Footprint for All Sites

Anaerobic Digestion

Courtesy of R Dale Richwine, MWH

Products of Anaerobic Digestion

• Yields gases and residues

• Gases used to make heat, electricity or fuel

• Produce Methanol (being done in Utah in large scale from pig manure fermentation).

• Residues used to make fertilizer

10

Courtesy of Mike Moore, OCSD

Why Anaerobic Digestion and Wastes are an Opportunity in California?

• 36 Million TPY disposed

• Potential to reduce GHGs

• Reduces reliance on landfills

• Alternatives to natural gas

• Helps achieve 33% threshold of renewable energy by 2020

• Low Carbon Fuel Standard (10% reduction in carbon intensity by 2020)

• 15% of waste stream is food waste - high value feedstock for digesters

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Courtesy of Michael Moore, OCSD

Types of Anaerobic Digester feedstock

12

Courtesy of Michael Moore, OCSD

RECOVERING & USING ENERGY FROM WWTP RESIDUALS

• To sell back to the grid as green power.

• To operate pumps and blowers used throughout the treatment process.

• To maintain optimal digester temperatures, dry the biosolids, and provide space heating for the WWTF.

US Wastewater Treatment Facilities (WWTFs) withAnaerobic Digestion & Off Gas Utilization

• # WWTFs in USA is 16,583• # WWTFs in USA treating a

wastewater flow > 5 MGD is 1,066 or ~ 6 % of total number

# of these with anaerobic digesters is 544# of facilities with anaerobic digesters that utilize biogas is 106

Source: 2004 Clean Watersheds Needs Survey

Current Situation / Potential

POTW anaerobic digester gas utilization for combined heat and/or power (CHP)If all 544 facilities install CHP:

• 340 MW of clean electricity generation,• 2.3 million metric tons of CO2, offset annually,• Equivalent to cutting emissions from 430,000

carsSignificant opportunities for savings in

energy costs

* Opportunities and Benefits of Combined Heat and Power at Wastewater Treatment Facilities, Combined Heat and Power Partnership, EPA 2006

Co-generation at Wastewater Treatment Plants in California

• ~ 50 % POTWs > 1 MGD have anaerobic digesters

• ~ 95 % of sewage treated, however, has its solids treated by anaerobic digesters

• Randomly interviewed 32 facilities21 have installed cogeneration (66 %)5 use methane for heat only 6 flare methane (20 %)

USEPA-Region 9, 2008

Wastewater Plant Diagram

PreliminaryTreatment

PreliminaryTreatment

SolidsReuse

SolidsDewatering

Central PowerGeneration System

Engines

Central PowerGeneration System

Engines

PrimaryTreatmentPrimary

TreatmentSecondaryTreatmentSecondaryTreatment

Effluent

Digesters

Influent

SolidsProcessing

SolidsProcessing

Anaerobic Digestion

InsolubleOrganics

Acid Formation

Acid Producers

OrganicAcids

Methane Formation

Methane Producers

MethaneCO2

Hydrolysis

SolubleOrganics

Biological (Extra-cellular Enzymes)

or Physical

(Heat & Pressure)

Simplified Process SummarySimplified Process Summary

Steve Arant, "Recent Advances in Biosolids Stabilization Case Histories," WEF/AWWA/CWEA Joint Residuals and Biosolids Management Conference and Exhibition, February 19-22, 2003, Baltimore, Maryland USA

Requirements for Anaerobic Digestion

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Typical Operational and Design Criteria for Thermophilic

Anaerobic Digestion as compared to Mesophilic Digestion

Typical Properties of Primary and Waste Activated Sludges

BTU Value of Different Types of Wastewater Treatment Residuals

Comparing Gas Production Capabilities of Different

Sources

From USEPA-Region 9 & EBMUD

Schematic of EBMUD Food –Waste Recycling Process

Example of Innovative Approach – EBMUD, CA

Diverting food waste from landfills prevents uncontrolled emissions of methane. Only 2.5% of food waste is recycled nationwide, and the principal technology is composting which produces volatile organic compounds and consumes energy. In California, approximately 137 wastewater treatment plants have anaerobic digesters, with an estimated excess capacity of 15-30% . Anaerobic Digestion of Food Waste funded by EPA-R9-WST-06-004.

Examples of Organizations Using Grease for Fuel/Energy

Schafer, P et al,2008

Waste Minimization / Conditioning Technologies

Courtesy of Tom Kutcher of CH2M Hill

Why Condition Sludge for Anaerobic Digestion?

• Solubilize sludge solids and lyse cells, thereby increasing the rate of degradation

• Render the non-degradable organic fraction degradable, thereby increasing the extent of degradation

• Ultimately result in the generation of less residuals to further manage

Thermal Hydrolysis

• High pressure-high temperature process: thermal hydrolysis of dewatered sludge under pressure using live steam.

• Hydrolyzed and pasteurized sludge digested at greater VSLRs (smaller vessels).

• Three systems:Cambi® Thermal Hydrolysis Process (THP)BioThelys® Process

Slide courtesy of Dru Whtilock, CH2MHill & WERF

CAMBI’s Performance Claims

Sludge Disintegration Processes

• Macerate sludge to homogenize• Increase pressure (12 Bar) with PC

pump• high pressure mixer, flow into

disintegration nozzle.• As the flow exits the nozzle, cavitation

occurs rupturing cell structure• Sludge can be passed through system

three times before discharge to the digesters.

Performance Data by Crown

Performance Data by Crown

Anna Maria Sundin, DISINTEGRATION OF SLUDGE - A WAY OF OPTIMIZING ANAEROBIC DIGESTION, Procs 13th European Biosolids & Organic Resources Conference & Workshop, www.european-biosolids.com

Micro-Sludge Process Flow Diagram

Rob Stephenson et al, “FULL SCALE AND LABORATORY SCALE RESULTS FROM THE TRIAL OFMICROSLUDGE AT THE JOINT WATER POLLUTION CONTROL PLANT AT LOS ANGELES COUNTY, “WEF/AWWA Joint Residuals and Biosolids Management Conference 2007

Summary of Sludge Pre-Treatment Options at JWPCP

Inland Empire, CA Digester Research

Fred Soroushian and Ufuk Erdal & Eliza Jane Whitman, ADVANCED DIGESTION TECHNOLOGIES IMPLEMENTATION AT INLAND EMPIRE UTILITIES AGENCY AND ENHANCED BIOGAS GENERATION, Procs. RESIDUALS AND BIOSOLIDS MANAGEMENT CONFERENCE 2006

Study Results

Digester Mixing Systems

After D. Parry for WEF/WERF/EPASolids Manual, March 2009

Discussion of Different Mixing Technologies

Kenneth D. Fonda, SHAKEN OR STIRRED: DIGESTER MIXING DESIGN AND OPERATION SUCCESSSTORIES, WEF/AWWA Joint Residuals and Biosolids Management Conference 2007

Discussion of Different Mixing Technologies

Discussion of Different Mixing Technologies

Typical Concentration Ranges for Anaerobic Digester Gas

Biogas Treatment for Beneficial Use

Problems with Siloxane

The sand-like material is SiO2 produced through oxidation (burning) of the volatized siloxanes contained in the digester gas. Figure shows siloxane deposition on boiler tubes.

Damage from H2S & Siloxane

Engine Generator is shown.

Treating Digester Gas with Activated Carbon

Combined Heat and Power

• Definition: Utilizing equipment to simultaneously generate electricity and heat using anaerobic digester biogas

Energy Recovery from Digester Gas using Boilers

Energy Recovery from Digester Gas using Engine

Generators

Energy Recovery from Digester Gas from a

Microturbine Unit

ELECTRIC & THERMAL ENERGY POTENTIAL WITH CHP FOR TYPICALLY SIZED

DIGESTER: MESOPHILIC

ESTIMATED CAPITAL COSTS FOR THREE CHP SYSTEMS

AT WASTEWATER TREATMENT FACILITIES

Case Study

From "The Power of Digester Gas: A Technology Review from Micro to Megawatts," Mark McDannel, Los Angeles County Sanitation Districts, WEFTEC, October 16, 2007

Case Study - LACSD

Power Generation Cost Summary Comparison

for Different Approaches

CHP Case Studies

• Albert Lee, MNFlow 2.82 MGDFuel Type – Digester gasPrime Mover – (4) 30 kW Capstone microturbinesEnergy savings – 800,000 kWh/yr (30%)Installed Cost - $250kAnnual energy savings - $40-$60kSimple payback - 4-6 yearsYear installed 2003

UPDATESOLIDS PROCESSING DESIGN AND

MANAGEMENT MANUAL

Manual Objectives

• Easy to update on CDs / online• Best management, technical

practices emphasis• Operator and Designer perspectives • Neutral on bioenergy sources

(thermal and biological) • Case studies, lessons learned,

example designs• Dated and location-specified cost

estimates• Cross-referenced

Online Version Available – WEFTECOctober 2010

Online Version Available – WEFTECOctober 2010

3rd Peer Final Review –3rd Peer Final Review –

1st Peer Draft Review – May 20091st Peer Draft Review – May 2009

2nd Peer Draft Review –2nd Peer Draft Review –

More than half way there!

TABLE OF CONTENTS

GLOSSARY OF TERMS (to be provided)CHAPTERS1. Introduction (Pramanik)2. General Considerations for Planning of Solids Projects (Shea, Moore & Stevens)3. Greenhouse Gas and Establishing Your Carbon Footprint (Baroldi & Cheng)4. Public Involvement (Beecher)5. Solids Production and Characterization (Gellner)6. Design Approach (Forbes)7. Conveyance (Sadick)8. Chemical Conditioning (Laraway, Cassell & Senss)9. Thickening (Gillette)10. Waste Minimization (Tsang)11. Anaerobic Digestion (Parry)12. Aerobic Digestion (Bizier et al)13. Dewatering (Essner & Koch)14. Composting (Williams, Todd)15. Alkaline Treatment (Smith)16. Disinfection and Stabilization Considerations (Naylor & Smith)17. Thermal Drying (Santha)18. Thermal Oxidation and Energy Recovery (Dominak)19. Other Thermal Processes (Chilson)20. Transport and Storage (Williams, Lisa)21. Management of Odors (Easter)22. Sidestreams from Solids Treatment Processes (Benisch)23. Instrumentation and Monitoring (Ekster & Lagrange)24. Land Application & Product Distribution (Moss)25. Landfill Management Systems (Sullivan)26. Emerging Technologies (Tsang)27. Treatment and Utilization of Green Gas (Schettler)

3. Greenhouse Gas and EstablishingYour Carbon FootprintLayne Baroldi, Orange County Sanitation District Stephanie Cheng, East Bay Municipal Utilities District

3. Greenhouse Gas and EstablishingYour Carbon FootprintLayne Baroldi, Orange County Sanitation District Stephanie Cheng, East Bay Municipal Utilities District

10. Waste MinimizationK. Richard Tsang, CDM

10. Waste MinimizationK. Richard Tsang, CDM

11. Anaerobic DigestionDavid L. Parry, CDM

11. Anaerobic DigestionDavid L. Parry, CDM

27. Treatment and Utilization of Green GasJim Schettler, Brown and Caldwell

27. Treatment and Utilization of Green GasJim Schettler, Brown and Caldwell

Questions?